Neurostimulation has become an accepted treatment for patients with chronic pain in their back and/or limbs who have not found pain relief from other treatments. In general, neurostimulation comprises applying an electrical current to nerve tissue in the pathway of the chronic pain. This creates a sensation that blocks the brain's ability to sense the previously perceived pain. There are two conventional forms of electrical stimulation commonly used to treat chronic pain: Spinal Cord Stimulation (SCS) and Peripheral Nerve Field Stimulation (PNFS). In SCS, electrical leads are placed along the spinal cord. A programmable implantable neurostimulator (INS) is implanted in the upper buttock or abdomen (under the skin) which emits electrical currents to the spinal cord via electrodes of the leads. Peripheral nerve field stimulation is similar to spinal cord stimulation, however peripheral nerve field stimulation involves placing the leads just under the skin in an area near to the peripheral nerves involved in pain.
A programmable INS requires circuitry for controlling the myriad of functions that are generally required to perform neurostimulation and a battery for powering such circuitry, as well as for providing the power necessary for generating neurostimulation signals. For example, a programmable INS can include an application specific integrated circuit (ASIC) for controlling the myriad of functions. However, an ASIC is relatively expensive to design, and typically requires a significant redesign whenever features are changed and/or added. For another example, a programmable INS can include an off-the-shelf central processing unit (CPU) that can be used to control the myriad of functions. This is beneficial because it provides for an off-the-shelf solution. However, if the CPU is not used in a power efficient manner, the use of the CPU can consume significantly more power than is practical, especially considering the desire to minimize the power consumed by the INS to thereby extend the useful life of the INS.